Motor-control system



Dec. 1924. v 519,255

5 A. L. HARVEY ET AL MOTOR CONTROL SYSTEM i l Filed Oct. 9. 1920 INVENTORS WITNESS S: Alb t L. Harry A. 4 1 W BY Dari; 11 Hunter ATTORNEY Patented Dec. 16, 1924.

UNlTED STATE-S PATENT OFFICE.

ALBERT L. HARVEY, F WILKINSBURG, AND DAVID H. HUNTER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

moroacomnor. SYSTEM.

Application filedOctober 9, 1920, Serial No. 415,816. Renewed May 14, 1924.

T 0 all whom it may concern."

Be it known that we, ALBERT L. IIARVEY, a citizen of the United States, and a resident "of Wilkinsbur in the county of Allegheny and State of Tennsylvania, and DAVID H. HUNTER, a citizen of the United States, and

a resident of vPittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new. and useful Improvementin Motor-Control Systems, of which the following is a specification.

. Our. invention relates to motor-control systems and it has particular relation to such s stems as are employed for starting induction and synchronous motors.

The object of our invention is to provide means for protecting .induction or synchronous motors from improper starting, especially where the starting operation is per formed by" manual operation of circuit breakers.

Heretofore, an induction motor has been started by closing a starting circuit breaker, which established a circuit between the lowvoltage terminals of an auto-transformer and the motor and afterwards opened the starting circuit breaker, and then closing a running circuit breaker which connected the motor directly to a supply source of energy. If the running circuit breaker was not closed within a relatively short interval of time after the starting circuit breaker had been opened, the speed of the induction motor would so decrease that, when the motor was connected directly to the source of energy, it would cause a dangerous electricaloverload upon the motor. i For a better understading of our invention, reference may be made to the accompanyin'g drawing- Figure 1 of which is a diagrammatic view of a motor-control system embodying our invention.

, Fig. 2. is a diagrammatic view. of a slightly "modified motor-control system embodying our invention.

Referring particularly to 1, an induction or synchronous motor 1, having a pri r'nary Winding2 and a secondary member 3, is

electrically connected, by a circuit comprising a knife-blade switch 4, to supply conductors 5. 7 An autotransformer .or other voltage-reducing device 6 and a starting circuit breaker 7 are employed to start'the motor 1.

A running circuit breaker 8, having a look ing device 9, is employed for connecting the 1 primary Winding 2 of the motor 1 directly to the source of energy. A'time-ele'ment relaylOand an auxiliary relay llcontrol the operation of the locking device 9 of the-running circuit breaker 8. 5 The starting circuit breaker 7 is actuated by an'arm' 12 which is pii otally mounted upon a pin 13. 1 The running circuit breaker 8 is actuated by anarm '14-'whiph ispivotally mounted upon a pin 15. The arm 14 is' provided witha handle 16. The locking device 9 of the circuit breaker 8 comprises a rod or bar 17 which is slidably mounted in a guiding member 18. v A projection v19 of L-shape extending from the arm T 14 may be brou ht into engagement with the rod 17 The "rod 17 may be actuated by a lever 21 whichfcomprises a member'22 of L-shape pivotally mounted upon a pin .23 mechanically connected to the bar 17 by] a pin 24- v p I A resilient member or spring 25a ,is secured to a stationary member or pin 26 and to the free end of the member 22 in. such way thatv it tends to force the bar 17 toward 3 the handle 16. of the circuit breaker 8. The respective ends of the bar 17 and the projection 19 on the arm 14 of the circuit breaker 8 are so designed that the circuit breaker 8 may be actuated to its open position, regard- 8 less of the condition of the remainder of the control system. The circuit breaker 8 may not be closed until the bar 17 has been withdrawn'sufiic iently to permit the projection 19 of the arm 14 to clear the end of the bar 17.

The member 22 of the lever 21 may be operated by energizing a coil 25, which actuates an armature member 26a. The armature member 261 is pivotally connected 9 to the member 22.

The motor 1 is started by first closing. the knife-blade switch 4 and then closing the starting circuit breaker 7. The primary winding 2 of the motor 1 is then energized 9 by a circuit established from the supply con ductors 5, through the knife switch 4, a set of conductors 28, auto-transformer 6,a set of conductors 29, which are connected to the low-voltage terminals of the auto-trans former ,conta ct members 30 of the starting circqjt breaker 7, and conductors 31 to primary winding 2 of induction motor 1.

The secondary member 3 of induction 5 motor 1i may be ener ized by induction from the member 2 thereo t or it may be energized from an independent source of direct cur rent, if it is a synchronous motor. After the motor 1 be ins to rotate and'itf has been brought to a desi rable speed, the starting circuit breaker 7 is' opened and the running circuit breaker 8 is closed.

The starting circuit breaker 7 and the run ning circuit breaker 8 are mechanically ip tje'rlocked by arod or bar 32, which is piyptal-ly. mounted upon a pin 33, and so .engages the arms 12 and 14 of the circuit breakeis'i' aud 8, respectively. that it is impossible for them to occupy their closed positions: at the same time. Therefore,

.gv, en the starting circuit breaker 7 has been J the running circuit breaker 8 can be closed until the starting circuit breaker as first been opened;

The starting circuit breaker 7 is provided .with an auxiliary'contact member 34 which establishes a circuit for energizing the actuating coil 35 of the relay 11, when the startin 'g circuit breaker 7 is closed. The circuit.

cprnprisingthe actuating coil of the re- ,lay lIand the auxiliary contact member 34 ofil the, starting circuit breaker 7. extends fro n one of the supply; conductors 28 ,fllrough conductor 3.6,contact member 34 of 35 starting circuit breaker 7, conductor. 37, ac tua t ingcoil 350i relayll, conductor 38. auxgliary contact member 39. of running circggrt breaker 8, and conductor to a second n2 coggluctor 28.

40 e actuatin coil 35 of the relay 11 being energized, t 1e relay 1-1 will close, thereby, establishing a holding circuit from one .o.f ,i th supply conductors 28 through conductors 36-and 42. contact member 43 of the .11, conductors 44 and 37. actuating:

35 of the relay l1, CQIldllQtOI 38, contact member 39 of running circuit member 8.

and conductor 40 to a second conductor 28.

ii: second circuit is also established, h

closing the relay 11. from one of the supply conductors 28 through conductors 36 and a2. cOntactinember 430i relay 11, condiu tlorsl' et t and 45, contact member 46 of timeel sin nt relay 10, actuating coil 25 of lock mg evice 9 of circuit breaker 8 and con ductors 47 and 40 to a second conductor 28.

actuating coil 25 of locking-device 9., Ling energized, causes the armature membei$260 to actuate the member 22 which. in

aim, will draw the bar 17in a direction away from the projection 19 of the arm 14 of the circuit breaker 8.

After the operator of the control system has: decided that the induction motor 1 has obtained suflicient operating speedfhe opens the starting circuit breaker 7 by manually actuating the arm l 2 thereof.

When the starting circuit breaker 7 has assumed its lower or open position, a circuit is established from the conductors through 79 conductor 36, contact membejr 3460fcircuitbreaker 7, conductor 49, actuating 'coil 50 of time-element relay 10, conductor 38, contact member 39 of running circuit breaker 8, and conductor 40, to conductors 28.

The actuating coil 50 of the time-element. relay 10 being energized, contact member-t6 will slowly rise until it breaks the circuit comprising the actuating coil 25 of the relay device 9 of the circuit breaker 8. The time 30 consumed by the relay lO before breaking this circuit is controlled by the dash pot 51 and the shape of the contact member 46.

vItis apparent that, once the starting circuit breaker 7 has opened, the running cir S5 cuit breaker 8 must be closed before the tizneelement relaylO occupies it-s open position. It the running circuit breaker S is not closed within this interval of time,.the actuating coil 25 will be de-energizedbythe relay 10 occupying its open positionand the arm 17 will then prevent the downward movement of the handle 16 of the circuit. breaker 8. It will then be necessary to repeat the operationsin the required order before-the motor can be brought. to,.full. speed.

\Vhen the circuit breaker 8 is closed. a circuit is established from supply conductors through knife-blade switch 4. set of conductors-52, contact members 53 o circuit breaker 8, and conductors 31, ,to .primary winding 2 of induction motor .1.

\Vhen the running. circuit breaker .8 is brought to its closed position, the auxiliary W5 contact member 39 thereof assumes its open a position. thereby breaking the circuit comprising the actuating coil 35 of the relay 11, thereby causing the relay 11 to open. When the relay 11 is opened, the actuating coil 25 of the locking device 9 of the circuit break- 01' 8 is tie-energized.

Referring to Fig. 2, corresponding apparatus and circuits are designated by the same numerals as in Fig. 1.

Time element relay 10 is provided with a contact member 46, similar to one Shown in Fig. 1 with the exception that itfis slidablv mounted on an armature member 54 and is positioned thereon by means of a resilient member 55 and a nut 56. The dash pot 51 is so arranged as to prevent quick downward movement of the armature member 54. The slow downward movement of the armature member 54 is at first compensated for by the spring which maintains the contact member 46 in its closed position. I

The operation of this system is begun, in the usual manner. by closing the knife-blade 1 from one of the conductors 28 through conductor 60, contact member 34 of the starting circuit breaker 7, conductor 61, actuating -o0il50oftime-element relay 10, conductor 62 to a second conductor 28.

whengthis circuit'is established, the actuating coil is energized, thereby causing the time-element .relay 10 to close. This operation may be arranged to consume a predetermined interval of time by adjusting thegrelay 710 in order that the armature member 54 shall have a slow upward movement. By having the time-element relay 10 slowly assume its closed position, too rapid opening of the starting circuit breaker 7 and closing, of the running circuit breaker 8 is prevented. r

1 s soon as the contact member 46 of the time-element relay 10 has assumed its closed position 'the actuating coil 25 of locking device ,9 of-pircuiqbrgaker 8 is energized by a circuit which is established from one of the conductors 28 through conductors and 64, contact member 46, actuating coil 25 and conductor to a second conductor 28. The actuating coil 25, being energized, causes the armature member 26 to disengage the bar 17 from the projection 19 of the arm 14. of the circuit breaker 8, and thus permits the circuit breaker 8 to be closed after the starting circuit breaker 7 has been opened.

As soon as the starting circuit breaker 7 has been opened, the actuating coil 50 of the time-element relay 10, is de-energized and the contact member 46 would quickly fall to its open position were it not for the compensating action of the resilient member 55. After a certain time has elapsed the resilient member 55 will no longer be able to maintain contact member 46 in its closed position because of the descent of the armature member 54.

Unless the circuit breaker 8 is closed before the time-element relay 10 is opened, the actuating coil 25 will be de-energized, and the locking device 9 will prevent the circuit breaker 8 from being opened. The motor 1 can then be brought to full speed only by repeating the operations that have been described.

It is apparent that, by constructing a motor-control system for induction or synchronous motors in accordance with our in vention, it will be impossible to start the motor improperly and that such a system gives full protection against closing a running circuit breaker, when an induction motor is idle, or when the motor is operatiug at such a low speed that it would be dangerous to connect it directly to the line.

lVhile we have shown our invention in a preferred form, it is apparent that minor modifications may be made in the apparatus employed and in the arrangement ofcircuits without departing from the spirit thereof. l-Ve desire, therefore, to'belimited only by the scope of the appended claims; 0

We claim as our invention: a

1. The combination with a dynamo-electric machine and a plurality-jot manually actuated switches, of means for preventing said switches from being closed simultaneously, and means for limiting the time'for closing one switch after opening another switch. 1 i I Y 2. In a motor-control system, the combination with a motor and a source of electricaluenergy, of a transformer, a manually actu- 85 ated starting switch for connecting [said motor to said transformer, a'manually actuated running switch for connecting said motor to said source, and meansfor limiting the time for closing said running switch after opening said starting switch.

in a motor-control system, the combina tion with a motor and a source of electrical energy. of a voltage-reducing device, a switch for connecting said motor to said voltage-reducing device, a second switch for connecting said motor to said supply source, means for preventing said switches from being closed simultaneously and means for locking said second switch in its open position to limit the time for closing said second switch after opening said first switch.

4. ln a motor-control system, the combination with a motor and a source of electrical energy. of an auto-transformer. a starting switch for connecting said motor to said transformer. a running switch for connecting said motor to said supply source, means for preventing said running switch from closing until after the opening of said startin; switch, and means, comprising a locking device and a time-element relay. for limiting the time for closing said running switch after said starting switch has been opened.

In a motor-control system, the combination with a motor and a source of electrical energy, of a transformer. a starting switch for connecting said motor to said transtorn'ier, a running switch provided with a locking device for preventing the closure thereof and a magnetic release therefor, means for preventing said switches occupy-- ing their closed positions at the same time. a time-clement relay for limiting the time between opening the starting switch and closing the running switch and means coacting with said starting switch for operating said relay.

6. In a m0torcontrol system, the combination with a motor and SOUITQ of electrical ener y, etatransformer, a startingcircuit rezrer for connecting said motor to said transformer, a running circuit breaker for connecting said motor to said supply source, I meansfor preventing said circuit breakers from occupying their closed positions simultaneously, alocking device for preventing itheiclosing ofsaid'running circuit breaker, ainagnetic'fre'lease for said locking device, a time elementrelay for controlling said magnetic release, aeontactorcontrolled by said startingeircuitbreaker for starting said re lay't'o' operate upon the closure of said startin' circuit breaker.

i'Tlie combination with a motor, of a manually actuated starting switch for ener *giz'ing said motor, a manually actuated running switch for increasing the energiza- -tio n of said motor, and means for preventing thecldsure of'said running switch to limit the"periodof' time between the opening of said starting switch andthe closing of said runniii 'g switch. I

8, The combination with a motor, and a source'o'f energy, of'an auto-transformer, a starting circuit breaker for connecting said motor to's aid auto t-ransformer, a running circuit breaker 'for connecting said motor to"sa id source-,Qa locking device for said voltage-reducing device,

zation of said releasing coil, and acontactor mechanically connected to said starting'circuit breaker for controlling the energization' of said actuating coil.

9. In a motor-control system, the combination with a motor, a source of energy, and-a of a starting'circuit breaker for connecting saiddnotofto said device, a running circuit breaker for connecting said motor to said 'source of energy, means for preventing said rtrnning circuit breaker from closing until afterfirst losing said starting circuit breaker for a predeterminedflinininium interval of "time and then opening said startingb'reaker, 'said ."V V means preventing breaker from closing breaker 18 not closed Wlllllfllfi predetermined said ining "circuit if 'said runnln'gbircuit period after opening said starting circuit breaker.

In testimony whereof, we have hereunto subscribed our names this first day 0f -OC- tober, 1920.

ALBERT L. HARVEY. DA I HUNTE 

